Electronegativity + Intermolecular Interactions + Periodicity

Question 1

Electronegativity

Answer 1

The ability of an atom to attract the bonding pair of electrons towards itself in a covalent bond

Question 2

Pauling electronegativity values

Answer 2

Used to compare the electronegativity of the atoms of different elements. By these values, the atom with the larger value is δ-

Question 3

What is the most electronegative element

Answer 3

Fluorine

Question 4

Key electronegative elements

Answer 4

N
O
F
Cl
Br

Question 5

Electronegativity across a period ➡️

Answer 5

Increases ⬆️

Question 6

Electronegativity down a group ⬇️

Answer 6

Decreases ⬇️

Question 7

δ meaning

Answer 7

Slightly

Question 8

Dipole bond when…

Answer 8

There is a great enough difference between electronegativity of atoms.

A dipole is the separation of partial charges in a molecule.
The separation of partial charges across a polar bond, arising

Question 9

Symmetrical molecules with Polar bonds

Answer 9

Permanent dipoles cancel out resulting in non-polar molecule (despite individual bond dipoles) (poalr if e- shared unequally)

Question 10

Symmetrical if…

Answer 10

NO lone pairs
All same bond type

Question 11

Asymmetrical if…

Answer 11

Has lone pairs
Different bond types present

Question 12

Intermolecular

Answer 12

Between molecules

Question 13

Instantaneous dipole

Answer 13

Where the bonded electron pair is shared unequally between the bonded atoms

Question 14

Induced dipole

Answer 14

A dipole formed due to it being next to an instantaneous dipole

Question 15

Induced dipole dipole interactions (London/Dispersion forces)

Answer 15

Weak intermolecular forces that exist between all molecules (polar or NP)

Question 16

Permanent dipole dipole interactions

Answer 16

Weak intermolecular forces that exist between the permanent dipoles in different polar molecules

Question 17

Van der Waals

Answer 17

Used to describe both induced dipole dipole and permanent dipole dipole intermolecular forces

Question 18

Hydrogen bonds

Answer 18

Type of permanent dipole dipole interaction found between molecules containing an electronegative atom with a lone pair of electrons (N, O or F) and a hydrogen attached to an electronegative atom in another molecule

Question 19

How does an induced dispose dipole interaction form

Answer 19

1. e- randomly move to 1 side of atom -> uneven distribution -> dipole
2. Dipole repels e- in next molecule -> dipole
3. Electrostatic attraction between + and - dipoles -> induced dipole dipole interaction
4. Temporary - force will disappear, return to non polar molecules

Question 20

All intermolecular forces are based on

Answer 20

Small electrostatic attraction between atoms which have been polarised in adjacent molecules

Question 21

Impact of number of e- on induced dipole dipole attraction

Answer 21

More e- = more energy to break intermolecular force = higher BP

Question 22

How are intermolecular forces measured

Answer 22

MP/BP
(Easily measured)

Question 23

Effect of molecule shape on induced dipole dipole interactions

Answer 23

Less branched = more points of contact between molecules = stronger induced dipole dipole interactions

Question 24

Molecules with permanent dipole dipole interactions also have…

Answer 24

Induced dipole dipole - these are present between ALL molecules
So more energy to overcome both rather than just induced

Question 25

Hydrogen bond if

Answer 25

H bonded to N/O/F -> permanent dipole between
N/O/F has available lone pair -> H attracted to LP

Question 26

Diagram of hydrogen bond includes…

Answer 26

• relevant delta +-
• labelled H bond
• dotted H bond
• lone pair of N/O/F shown (:)
• 180 degree H bond (semi circle around H)

Question 27

Why is ice less dense than water

Answer 27

In ice H bonds hold molecules in fixed position but molecules must be less tightly packed than water to fit 3D structure (resembles diamond) of ice

Question 28

Unusual BP of water

Answer 28

Higher than expected - similar sized molecules with a less electronegative atom tend to be gases at RT

Question 29

Soluble in water if…

Answer 29

Molecule can create H bond with water
(More/stronger H bonds = more soluble)

Question 30

Periodicity

Answer 30

Repeating pattern of trends in physical + chemical properties across different periods

Question 31

First ionisation energy

Answer 31

Energy required to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions. kJmol-1

Question 32

Second ionisation energy

Answer 32

Energy required to remove 1 electron from each ion in 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions. kJmol-1

Question 33

Successive ionisation energy

Answer 33

A measure of the energy required to remove each electron in turn